Method of preparing pavement composition



Patented June 17, 1930 UNITED STA MELDRUM D. SHANNON, OF SACRAMENTO, CALIFORNIA METHOD OF PREPARING PAVEMENT COMPOSITION No Drawing.

The invention relates to a method of preparing a bituminous pavement composition and has for its objects to provide a pavement composition which is extremely durable under continued usage, economical of manufacture and which adheres with a maximum tenacityto different characters of bases or foundations on which it islaid.

A further object of the invention is to provide a road of pavement composition which may be applied with equal facility to a base of concrete, cement, or wood flooring or pavement, without the necessity of interposing a coating of adhesive material, and this is made possible by reason of the nature and mode of preparation of the improved composition.

A further object of the invention is to provide a pavement composition of high wear-resisting qualities and which may be used to equal advantage for either outdoor or indoor purposes.

A further object of the invention is to provide a pavement or flooring composition of the character described, the long, durability and high wear-resisting qualities of which are largely due to the increased temperature at which the materials are combined and mixed, and which high temperature it has been found disadvantageous to employ in past and present road and floor building practice.

A further object of the invention is to provide a paving and flooring material which is elastic and which is capable of contracting and expanding without altering or impairing its desirable qualities.

A further object of the invention is to provide a paving material which is fireproof, acid-proof, and a non-conductor of electricity, with the result that it is especially adaptable for a wear-resisting composition suitable to be laid as a flooring surface in factories, warehouses, and the like.

It has been found in prior practice of laying bituminous pavements and flooring surfaces of the general character contemplated by the present invention, that engineers and contractors have agreed that the asphalt should not be heated to over three Application filed June 16, 1925. Serial No. 37,581.

ticity is destroyed, its viscosity impaired and the volatile oils eliminated or materially reduced. In preparing and laying the composition contemplated by the present invention, the best results are obtained by heating the composition, including the asphalt and other combined ingredients as a mixture, to at least three hundred and eighty (380) degrees Fahr. and more advantageous results are obtained when it is heated as high as four hundred and twenty-five (425) degrees F ahr. This relatively higher temperature obtained by the present invention, and which has heretofore been deemed im practicable, is not attended by any of the disadvantages, above set forth and heretofore experienced, and due to the increased temperature herein obtained the material is more intimately mixed and adheres more firmly to the wood or concrete base on which it is laid. It is extremely diflicult to remove because it tends to adhere firmly to the wood fiber or cement, and this extremely high tenacity of the pavement composition toward the base is effected by heating the material to the relatively higher tempera tures above outlined, such temperatures. of preference not exceeding four hundred and twenty-five (425) degrees Fahr. No ntervening coating of paint or other material is necessary to effect the union between the pavement and the board or base, as has been necessary in other forms of asphalt or bituminous pavement.

With such objects in view, as well as other advantages which may be incident to the use of my improvements, the invention consists in the combination of ingredients and manner of making the same, which are hereinafter set forth and claimed, with the understanding that the several necessary elements and steps of procedure which constitute the same may be varied in proportions without departing from the nature and scope of the invention.

The improved pavement composition which provides the road or flooring. surface having the qualities and advantages above set forth, is preferably composed of the following raw ingredients of the nature and character described and which are proportioned and combined in the manner hereinafter specified.

Asphaltz'c 0ement.The asphaltic cement consists preferably of any standard asphalt, free from admixture with any residues obtained by the artificial distillation of coal, coal tar, or parafiine oil. It is preferably soluble in carbon disulphide to the extent of at least 99 percent, and in carbon tetra chloride to the extent of not less than 28 percent. The asphaltic cement preferably should have a penetration of not more than forty-five degrees, District of Columbia standard.

Limest0ne.The mineral filler preferably consists of a limestone powdered or pulverized to such degree of fineness that it will entirely pass through a fifty mesh to the inch screen and a minimum of sixty-six sharp grade, and should contain not more percent should pass through a two hundred mesh to the inch screen.

SamL-The sand consists preferably .of the clean, hard grained and moderately than three percent of mica, loam, clay, or other earthy impurities. It should of preference contain not less than three percent of moisture.

R00k.The broken stone ingredient preferably consists of clean, hard, and tough rock which should be free from disinte rated material. It is desirable that all 0 the broken or crushed rock should pass through a three-eighths inch mesh screen.

An enduring wear-resisting pavement or flooring surface consisting of the above ingredients and possessing other desirable attributes above set forth, is preferably or may be prepared by combining and mixing the respective ingreQents by weight within the following proportions? (1) Asphaltie cement between 8 and 20 percent.

(2) Finely pulverized stone dust or powdered limestone between 11 and 25 percent. (3) Sand between 18 and 55 percent.

(4) Crushed rock between 14 and 45 percent.

The paving composition may be prepared directly in the vicinity of the road, pavement or flooring to be laid, and the procedure consists in combining and mixing the above ingredients within the proportions specified, in' 4 a rotary drum. The drum is provided with seventy-five (375) and four hundred and twenty-five (425) degrees Fahn, and it is desirable that the material be delivered from the drum without coming in contact with the flue gases from the fire box.

The composition is laid on or applied to the surface or flooring to be paved while the latter. is clean and dry, and effective results are obtained by laying the paving composition in a uniform thickness of approximately three-fourths of an inch. The thickness of the paved surface, however, may be varied according to prevailing conditions. If desired, the mixture may be conveyed from the drum to the surface to be paved in a suitable cart or dump truck, it being desirable that the temperature of said mixturebe not lower than three hundred and twentyfive (325) degrees Fahr. at the time it is applied to the surface or base.

In constructing the road, pavement or flooring surface, the composition is prepared as above outlined, is then uniformly spread over the foundation by means of suitable rakes or implements, and is preferably finished to a true and level surface by means of a straight edge. If desired, the material may be of such'consistency that it will float into position and after hardening, a suitable roller may be used for smoothing. A small amount of powdered limestone or cement may be thereafter dusted over the surface. The resulting pavement produces a close grained, level, smooth surface of a durable, high wear-resisting quality, possesses a high degree of tenacity or capacity to adhere to the base or foundation, and is free from all depressions and inequalities.

If desired, the improved paving or flooring composition may be prepared by means of a rotary drum heated to the above described relatively high temperature and utilizing most of the ingredients in the proportions specified, but omittingthe broken rock. It has been found in practice that an enduring and otherwise satisfactory pavement or flooring may be obtained by the use of asphaltic cement, powdered limestone, and sand alone, when prepared in the manner and proportions above set forth.

It 'will be understood that the improved and enduring wearing surface, which is provided by preparing the ingredients accord ing to the procedure outlined, is largely effected by reason of the relatively high temtween 8 and 20 per cent by weight of as halt, between 11 and 25 percent by weig t of perature of between three hundred and sev- .powdered limestone, between 18 and perent -five (375) and four hundred and twen-' tyvs (425) degrees Fahr. to which the materials are subjected when intimately combined. This increased and relatively higher temperature over rior practice produces a paving surface whic is extremely adherent to the base or foundation on which it is laid. It is especially adherent, by reason of its method of preparation and a plication, to a base of wood or 'fiber, t ereby rendering the paving composition especially adaptable for covering wooden brid es, factory floorings and the like. In 0 taining the above described results, an asphaltic cement below forty-five (45) degrees penetration is preferably employed. in the composition.

' Satisfactory results have been obtained without the necessity of rolling, tamping, or otherwise compressing the pavement after it has been laid, and this is due to the thorough and intimate mixture of the ingredients at the relatively high temperaturedescribed. In the event that it is desired to use a roller for smoothing the finished pave-' ment, a small hand roller weighing not over 500 pounds is sufficient to finally finish the surface.

While the improved composition has been described as particularly applicable for road and pavement surfaces, itis to be understood that the same may be applied with equal satisfactory results as a roofing composition. The material is particular useul on flat roofs where a waterproo fireresisting and long wearing surface is essential and desired. In addition to the useful advantages above set forth, the improved composition is proof against acids, vermin, and does not corrode or crumble away under continued and heavy usa e when employed as a building or factory ooring.

What I claim is:

1. The method of preparing a pavement composition which consists in combining a mixture of asphalt, powdered limestone, and sand containing .not less than 3 percent of moisture, said materials being thereafter I subjected to a temperature in excess of 375 degrees Fahr.

same to a temperature of substantially 375- degrees Fahr. and until practically all steam 2. The method of producing a pavement and flooring compos1tion which comprises pre aring and combinin a mixture of aspha tic cement, powdere limestone, broken rock and sand containing'substantially three pzrcent or more of moisture, said materials ing intimately combined by subjecting the has been driven off the product.

3. The method of preparing a pavement composition which consists in combiningbe- 

